Biomass is generally defined as living and recently dead biological material which is capable of being used as a renewable fuel for purposes of energy production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibers, chemicals, or heat. Biomass may also include biodegradable wastes that can be burned as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been “out” of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.
Biomass is grown from several plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sugarcane, and oil palm (palm oil). The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing. The nature of biomass material presents various obstacles, however, to the wide-scale commercial use of biomass for energy production.
One of these obstacles stems from the fact that biomass normally has very high moisture content—about 50% to 80%, or even higher—which results in a low BTU value per unit weight of biomass. (The term “BTU” is used to describe the heating value or energy content of fuels.) The low heating value in turn hampers combustion, which renders energy production from biomass an inefficient process. Accordingly, capital investment in biomass combustion equipment is often cost-prohibitive and impractical for commercial energy production.
Another obstacle to commercial use of biomass for energy production is that biomass is normally lighter and less dense than traditional fossil fuel (i.e., the biomass is fluffier). The low density of biomass is attributable to a large void space typical of biomass material. At present, the delivered BTU per dollar cost of biomass is economically unfavorable compared to the BTU per dollar cost associated with energy production from traditional fossil fuels. The unfavorable economics of biomass-to-energy conversion arising from the large void space and low density of biomass material makes shipping large amounts of biomass BTUs very costly and impractical for energy production.
Yet another obstacle is the difficulty in storing biomass. Biomass tends to rot or degrade quickly; it has a relatively short shelf life. The consequent need to process biomass quickly limits handling options and undermines the economic viability of using biomass commercially. A further obstacle is that some biomass, particularly herbaceous biomass, is very high in water-born alkalinity which can harm traditional furnaces and boilers. This alkalinity renders herbaceous biomass impractical as a source of fuel for energy production.
Accordingly, there is a pressing need to increase the amount of energy per unit weight of biomass. There is also a pressing need to convert biomass to a solid fuel economically and practically. There is also a pressing need to improve the efficiency of generating electrical energy from biomass.